Dual frequency dual polarization horn antenna



DUAL FREQUENCY DUAL POLARIZATION HORN ANTENNA Inventor WILL/AM S/C'/Ak By dij/@A0- Agent `lune 28, 1960 Filed Nov. l, 1957 W. SICHAK `lune 28, 1960 DUAL FREQUENCY DUAL PoLARIzATIoN HORN ANTENNA Filed Nov. 1, 1957 2 Sheets-Sheet 2 lll/ll l/l/ l/ l.

UnitedStates Patent DUAL FREQUENCY DUAL POLARIZATION HORN ANTENNA William Sichak, Nutley, NJ., assignor to International Telephone and Telegraph Corporation, Nutley, NJ., a corporation of Maryland Filed Nov. 1, 1957, Ser. No. 693,974

14 Claims. (Cl. 343-756) This invention relates to antennas and more particularly to an antenna of the horn type responsive to two separated frequency bands.

Throughout the specification, the antenna will be described in terms of a transmission antenna, but it is to be understood that the antenna is a reciprocal device and can be utilized to receive the same type of energy in substantially the same manner.

Antennas capable of operating at two different frequencies broadly are not new in the antenna art. The prior art disclosed that horn-type antennas have been used to transmit and receive signal waves in widely separated frequency bands. This has been accomplished in the prior art by employing energizing means judiciously positioned within the end of a single waveguide ared at both the horizontal and vertical dimensions. The two signals of different frequencies are radiated with their polarizations crossed in order to substantially reduce interaction therebetween.

It is well known that to provide linearly polarized waves, the horn antenna may be fed with TEOl and TELO waves of different frequency, that is, one wave will have vertical polarization of the electric field intensity, and the other a horizontal polarization of the electric field intensity. Both waves of course have a component of magnetic force in the direction of propagation. To support the horizontally polarized wave (TELO), the vertical dimensions of the single waveguide of the prior art must be larger than the critical dimension which is determined by the operating frequency of the wave. That is, the vertical dimension of the waveguide must be greater than a half wavelength at the operating frequency (the frequency of the TELO wave). The horizontal dimension of the waveguide may be arbitrarily chosen as far as the T ELO wave is concerned. Similarly, the TEO, wave which results in a vertically polarized wave requires that the horizontal dimension of the waveguide must be larger than the critical dimension. As before, this horizontal dimension is greater than a half wavelength at the operating frequency of the vertically polarized wave. The vertical dimension of the waveguide may be arbitrarily chosen as far as the TEOJ wave is concerned.

Thus, the vertical and horizontal dimensions of a horn antenna employing a single waveguide rnust be chosen to satisfy the radiation of two waves of different frequencies which results in the horn antenna responding differently to the two frequency bands. This means that for one frequency band the radiation pattern will be different than the radiation pattern of the other frequency band. Since the dimensions of the single waveguide are interrelated, it is substantially impossible to adjust the radiation patterns by flaring the aperture to be substantially identical. This is a decided disadvantage in certain communication systems and particularly in certain radio diversity systems where it is desired to have the signal of the two frequencies correspond as closely as possible in their radiation patterns so that substantially the same area is covered by each signal. Other com- Patented June 28, 1960 munication systems may require completely different radiation patterns with complete freedom of independent adjustment of the radiation patterns of each frequency being radiated.

It is, therefore, an object of this invention to provide an improved antenna responsive to signals of two separate frequency bands substantially overcoming disadvantages of the prior art arrangements.

Another object of this invention is to provide an antenna where the radiation patterns of the signals of two separate frequency bands may be independently controlled.

A feature of this invention is the provision of an antenna comprising a rst waveguide dimensioned to be responsive to a rst wave energy of given polarization in a first frequency range and a second waveguide dimentioned to be responsive to a second wave energy of a polarization horizontally related to said given polarization in a second frequency range separated from said first frequency range. The second waveguide is disposed within and coextensive with said first waveguide in a substantially non-interfering relation with the energy propagated in said first waveguide.

Another feature of this invention is the provision of a rectangular waveguide being dimensioned to support vertically polarized waves in a first frequency range and at least one pair of coplanar fins supported at their outer edges in the vertical surface of the rectangular waveguide and horizontally spaced at their inner edges from each other to provide in conjunction with the horizontal surface of the rectangular waveguide or an effective extension thereof a horizontally polarized wave in a second frequency range spaced from said first frequency range, the vertical spacing between the fins and the horizontal surfaces of the rectangular waveguide being less than one-half wavelength at the operating frequency in said second frequency range.

Still another feature of this invention is the flaring of the rectangular waveguide for adjustment of the radiation aperture for the vertically polarized wave occurring in the rst frequency range and the flaring of the horizontal spacing between the coplanar fins to provide an adjustment of the radiation aperture of the horizontally polarized wave independent of the dimensions of the rectangular waveguide.

The above-mentioned and other features and objects of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a top plan view of an embodiment of the antenna arrangement following the principles of this invention;

Fig. 2 is a cross-sectional view taken along line 2-2 of Fig. l;

Fig. 3 is an end view of Fig. 1;

Fig. 4 is a top plan view of another embodiment of an antenna following the principles of this invention;

Fig. 5 is a cross-sectional view taken along line 5-5 of Fig. 4; and

Fig. 6 is an end view of Fig. 4.

Referring to Figs. l to 3, the antenna of this invention responsive to two frequency bands is illustrated as comprising a first waveguide 1 dimensioned to be responsive to vertically polarized wave energy in the lower of the two frequency bands, such as in the frequency band 960 to 1450 megacycles, and a second waveguide 2 dimensioned to be responsive to horizontally polarized wave energy in the higher of the two frequency bands, such as in the frequency band 2200 to 3300 megacycles. Waveguide 2 is illustrated to be disposed within and sub-V stantially coextensive with at least a portion of waveguide 1,

More specifically, the antenna of this invention includes a rectangular waveguide 3 as the lirst waveguide 1 whose horizontal dimension d1 is the critical dimension for vertically polarized wave energy, this is, greater than one-half wavelength at the operating frequency in the operating frequency band. Waveguide 3 has a portion 4 adjacent one end thereof whose vertical dimension d3 is flared in a predetermined amount to provide a desired radiation pattern, the amount of flaring lending itself to adjustment to thereby control the radiation pattern of the vertically polarized wave. This arrangement thereby provides a horn antenna for radiating a signal in the lower of the two operating frequency bands.

In accordance with the principles of this invention, a second waveguide, waveguide 2, is provided within waveguide 3 for radiation of a radiation pattern in the higher of'the two frequency bands. Waveguide 2 comprises a plurality of pairs of coplanar tins 5 and 6. The outer edges 7 of ns 5 and 6 are secured to the vertical walls of waveguide 3 such that the vertical spacing therebetween, dimension d5, is below cutoff, that is, less than one-half wavelength at the operating frequency. The ins 5 and 6 have their inner edges 8 spaced horizontally a predetermined amount to provide passage of wave energy. As pointed out hereinabove, for horizontally polarized waves, the spacing between the edges 8 of fins 5 and 6 is not critical. The vertical dimension d2 of the second waveguide 2 must be such that it is greater than one-half wavelength at the operating frequency in the higher of the two frequency bands to support the horizontal polarization of this wave energy. As depicted in Figs. 1 to 3 vand Figs. 4 to 6, the vertical dimension of waveguide 3 is made to correspond to the critical dimension d2 for the second waveguide 2. To maintain this dimension constant through the tiared portion 4 of waveguide 3, there is provided a first plurality of rods 9 disposed above fins 5 and 6 and a second plurality of rods 9 disposed below tins 5 and 6 to behave as a continuation of the horizontal walls of waveguide 3. To provide this continuation of the horizontal walls of waveguide 3, the spacing, d5, between rods 9 is less than one-half wavelength at the operating frequency of the horizontally polarized wave.

The plurality of pairs of coplanar iins S and 6 and rods 9 are disposed normal to the electric field of the vertically polarized or lower frequency waveguide mode in waveguide 3 and, hence, will not appreciably disturb this waveguide mode. Hence, the electric field for the horizontally polarized higher frequency waveguide mode is bounded by the inner edges 8 of fins 5 and 6 which are vertically spaced below cutoff and the top and bottom of waveguide 3 or the extension thereof provided by rods 9. This arrangement constitutes waveguide 2.

A portion of fins 5 and 6, substantially coextensive with ared portion 4 of waveguide 3, generally indicated at 10, is iiared to provide an adjustment of dimension d., and, hence, the radiation pattern of the horizontally polarized wave. This adjustment is independent of the adjustment provided for the vertically polarized wave by adjusting the flaring of portion 4. Thus, the primary pattern from each horn can be controlled for each frequency band with the primary patterns of the two frequency bands having a common focus point substantially located atthe smaller end of the flared portions. It will be noted that the dimensions d., and d1 and the dimensions d3 and d2 are independent of each other and, therefore, no interaction results between the two radiation patterns and one may be adjusted without affecting the other.

The above description and the illustration in the drawings illustrate the employment of three pairs of coplanar fins 5 and 6. 1t is to be understood .that this is for only one set of operating frequency bands. Under certain other conditions of operating frequency bands it would be possible for the antenna to function as described above with one, two, four or tive pairs of fins 5 and 6 depending upon the operating frequencies of the cross polarized wave energy. It is to be remembered that the dirnensions d5 and d6 must be below cutoff at the operating frequency of the horizontally polarized wave. The above description and illustration in the drawings disclose that rods 9 behave as extensions of the horizontal walls of waveguide 3 which constitutes a portion of the boundaries of the second waveguide. It is to be understood, however, that the rods 9 or an equivalent structure can act as the complete boundary of waveguide 2 disposed l throughout the length of waveguide 3.

Applicant has illustrated in his drawings two sets of iigures, Figs. l, 2 and 3 constituting one set of drawings illustrating one particular arrangement of coupling the polarized waves to his novel antenna arrangement, while Figs. 4, 5 and 6 illustrate a second arrangement for coupling the polarized waves to substantially the same antenna arrangement. In Figs. 1 to 3, a means 11 is coupled in longitudinal alignment with waveguide 3 to launch into or receive from waveguide 3 a vertically polarized wave. Means 11 may be a vertically disposed probe in a waveguide which lis a continuation of waveguide 3 generally shown at 11a. In the embodiment of Figs. l to 3, a means 12, such as a horizontally disposed probe in waveguide 12a, is provided to launch into or receive from waveguide 2 a horizontally polarized wave. Means 12 and waveguide 12a are illustrated as being at right angles to waveguide 2 and also waveguide 3. A broadband right angle bend 13 formed by configuring the horizontal spacing between the inner edges of ns 5 and 6 is provided as a transition means between waveguide 2 and waveguide 12a, both of these waveguides having substantially the same dimensions.

Figs. 4 to 6 illustrate the second arrangement for coupling the polarized waves to the various components of the antenna system described in detail in connection with Figs. 1 to 3. Figs. 4 to 6 have applied to the components of the antenna system the same reference characters employed in connection with Figs. l to 3, since the antennas of these two embodiments are substantially identical. The vertically polarized waves in the embodiment of Figs. 4 to 6 are launched from a transducer 14 which is disposed at right angles to waveguide 3 parallel to the vertical walls of waveguide 3 to thereby excite the lower frequency vertically polarized wave in waveguide 3. The high frequency horizontally polarized waves are coupled to waveguide 2 by means 15, such as a horizontally disposed probe in waveguide 16, which has the same vertical and horizontal dimensions as waveguide 2'. Thus, the waveguide 2 is extended longitudinally of waveguide 3 to the means 15 while the vertically polarized launching means 14 is at right angles to waveguide 3.

The above description has disclosed two arrangements for launching the polarized waves for the operation of the antenna of this invention. It is within the scope of this invention to employ other arrangements to launch polarized waves into the novel arrangement of this antenna which is responsive to two separate frequency bands and where the radiation patterns of each frequency band may be independently adjusted.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

I claim:

l. An antenna comprising a first uniconductor waveguide having a horizontal dimension to support a vertically polarized wave in a rst frequency range and a second uniconductor waveguide having a vertical dimension to support a horizontally polarized wave in a second frequency range separated from said rst frequency range, said second waveguide being disposed within and substantially coextensive with said first waveguide in a substantially non-interfering relation with the wave supported in said first waveguide, said second waveguide including a first plurality of conductive elements disposed in a given plane supported between the vertical surfaces of said first waveguide spaced from each other by less than one-half wavelength at the operating frequency of said second waveguide and a second plurality of conductive elements disposed in a plane parallel to said given plane supported between the vertical surfaces of said first waveguide spaced from each other less than onehalf wavelength at the operating frequency of said second waveguide, said first and second plurality of conductive elements being spaced by said vertical dimension.

2. An antenna comprising a first uniconductor waveguide having a horizontal dimension to support a vertically polarized wave in a first frequency range, said first waveguide having an end portion fiared a predetermined amount in the vertical dimension to provide a given radiation pattern for said vertically polarized wave and a second uniconductor waveguide having a vertical dimension to support a horizontally polarized wave in a second frequency range separated from said first frequency range, said second waveguide having an end portion fiared a predetermined amount in the horizontal dimension to provide a given radiation aperture for said horizontally polarized wave, said second waveguide being disposed within and substantially coextensive with said first waveguide in a substantially non-interfering rela tion with the vertically polarized wave of said first waveguide, said first waveguide including a rectangular waveguide having horizontally and vertically disposed walls and said second waveguide includes at least two coplanar fins having their outer edges secured to the vertical walls of said first waveguide and their inner edges spaced from each other a given amount, a first plurality of conductive elements supported between the vertical walls of said first waveguide spaced from each other by less than onehalf wavelength at the operating frequency, and a second plurality of conductive elements supported between the vertical walls of said first waveguide spaced from each other by less than one-half wavelength at the operating frequency of said second waveguide, said first and second plurality of conductive elements being spaced by the vertical dimension of said second waveguide and disposed on opposite sides of said coplanar fins in a spaced relation therefrom less than one-half wavelength at the operating frequency of said second waveguide to provide a waveguiding passage defined by the spacing of said first and second plurality of conductive elements and the inner edges of said coplanar fins.

3. An antenna according to claim 2, wherein a portion of the inner edges of said coplanar fins are tapered outwardly to provide the radiation aperture for said second waveguide.

4. An antenna according to claim 2, wherein the horizontal walls of said first waveguide are spaced to provide the vertical dimension of said second waveguide and said rst and second plurality of conductive elements provide an extension of the horizontal walls of said first waveguide into the flared end portion thereof.

5. An antenna according to claim 4, wherein a portion of the inner edges of said coplanar fins are tapered outwardly to provide the fiared end portion of said second waveguide.

6. An antenna according to claim 5, wherein the tapered inner edges of said coplanar fins are coextensive with the flared end portions of said first waveguide.

7. An antenna comprising a first uniconductor rectangular waveguide having a horizontal dimension to support a vertically polarized wave in a first frequency range, a first and a second plurality of conductive rods supported between the vertical surfaces of said first waveguide, the rods of each plurality of rods being spaced from each other less than one-half wavelength at an operating frequency disposed in a second frequency rangeA spaced from said first frequency range, said first and second plurality of rods being spaced from each other vertically to support horizontally polarized waves of said second frequency range, and a plurality of spaced pairs of coplanar fins disposed between said first and second plurality of rods, each of said pairs of fins having their outer edges supported in the vertical surfaces of said first waveguide and their inner edges spaced from each other a given amount, the spacing between said pairs of fins and said first and second plurality of rods being less than one-half wavelength at the operating frequency of said horizontally polarized waves, the inner edges of said pairs of fins and said first and second plurality of rods cooperating to provide a second uniconductor waveguide substantially coextensive with said first waveguide to support said horizontally polarized wave.

8. An antenna according to claim 7, wherein an end portion of the inner edges of said coplanar fins are fiared a predetermined amount to provide a given radiation aperture for said horizontally polarized wave and an end portion of said rectangular waveguide is fiared a predetermined amount in the vertical dimension to provide a given radiation aperture for said vertically polarized wave.

9. An antenna according to claim 8, wherein the fiared end portion of said coplanar fins is independent of but co-extensive with the fiared end portion of said rectangular waveguide.

l0. An antenna comprising a first uniconductor waveguide dimensioned to be responsive to a first wave energy having a given plane of polarization in a first frequency range and a second uniconductor waveguide dimensioned to be responsive to a second wave energy having a plane of polarization orthogonally related to said given plane of polarization in a second frequency range separated from said first frequency range, said second waveguide being disposed within said first waveguide and coextensive with a given portion thereof in a substantially non-interfering relation with the energy propagated in said first waveguide, said second waveguide including first conductive means disposed in a first plane perpendicular to said given plane of polarization disposed between and supported from the walls of said first waveguide parallel to said given plane of polarization and second conductive means disposed in a second plane spaced from and substantially parallel to said first plane disposed between and supported from the walls of said first waveguide parallel to said given plane of polarization, the distance between said first and second conductive means being different than the distance between the walls of said first waveguide perpendicular to said given plane of polarization to enable adjustment of the radiation pattern of said first waveguide independent of the dimensions of said second waveguide.

l1. An antenna according to claim 10, wherein the walls of said first waveguide perpendicular to said given plane of polarization are fiared to provide a given aperture for said first waveguide and said second waveguide includes at least one conductive body supported from each of the walls of said first waveguide parallel to said given plane of polarization intermediate said first and second conductive means, said conductive bodies establishing wave energy confining surfaces parallel to said given plane of polarization fiared to provide a given aperture for said second waveguide independent of the dimensions of said first waveguide.

12. An antenna according to claim 10, wherein the vertical walls of said first waveguide are spaced a given horizontal distance to support vertically polarized wave energy in said first frequency range and said first and second conductive means are disposed between and supported from the vertical walls of said first waveguide and polarized wave energy in said second frequency range.

, 13. An antenna according to claim l2, wherein said iirst waveguide includes a first end portion, the horizontal walls of said first waveguide having a ared portion within said first end portion to provide given radiation aperture for said vertically polarized wave energy and s aid second waveguide includes a second end portion and at least one conductive body supported from each of the vertical walls of said first waveguide intermediate said iirst and second conductive means, said conductive bodies establishing vertical wave energy confining surfaces having a flared portion within said second end portion to provide a given aperture for said horizontally polarized wave energy.

14. An antenna according to claim 13, wherein said rst end portion is coextensive with said second end portion.

References Cited in the file of this patent UNITED STATES PATENTS 2,364,371 Katzin Dec. 5, 1944 2,825,060 Ruze Feb. 25, 1958 FOREIGN PATENTS 890,388 France Nov. 2, 1943 OTHER REFERENCES Pub. (1), Dual-Mode Horn Feed for Microwave Mul- 15 tiplexing, Electronics, September 1954, pp. 162-164. 

